Study On The Interfacial And Emulsifying Properties Of ?-lactoglobulin Fibril/Typical Food Components

Protein fibril aggregates(?-lactoglobulin fibril,BLGF)were self-assembled product of protein under certain conditions.As a new functional food materials,it has potential application value in food industry.In this thesis,interaction between BLGF and other classical food components,such polysaccharide,phospholipids and protein,was investigated,and further the interfacial and emulsifying properties of the complex were studied.The main conclusions were as follows:1.Fibrillation of ?-lactoglobulin at pH 2.0 and low ionic strength could be divided into three parts: lag phase period,growth period,and mature period.Fibrillation could significantly improve the surface activity and emulsifying properties of ?-lactoglobulin.Product of the 2 hours fibrillation could form an emulsion with smallest droplet size(8.8 ?m),while the product of the 0.5 hours fibrillation could obtain the most stable emulsion.2.Interaction between ?-lactoglobulin fibrils(BLGF)and dipalmitoyl phosphatidylcholine(DPPC)and its effect on the interfacial and emulsifying properties of BLGF were investigated at pH 7.0.Incorporation of a small amount of DPPC(BLGF/DPPC ratio < 1:10000)led to the formation of brush-like complexes in which the fibrils were partially coated with a layer of DPPC.This interaction mode was favorable for the adsorption of fibrils onto the oil-water interface,resulting in a thicker and protruding interfacial layer with higher viscoelasticity.On the contrary,incorporation of excessive amount of DPPC(BLGF/DPPC ratio > 1:10)led to the formation of pearl-necklace-like complexes in which the fibrils were heavily and irregularly coated with DPPC surface micelles.This interaction mode tended to reduce the adsorption of fibrils onto the oil-water interface and thus impair the resulting interfacial viscoelasticity.Emulsifying performance of BLGF/DPPC complexes was found to be related to the different interaction modes and interfacial properties.The incorporation of a small amount of DPPC helped to reduce the particle size of BLGF-stabilized emulsions,whereas a high loading of DPPC gave coarse and unstable emulsions that destabilized within one-week storage at ambient temperature.3.Formation and interfacial properties of the electrostatic complex of BLGF and seyal were studied at pH 3.5.When the fibril content was less than 9.09% wt.,a high charged soluble BLGF/Seyal complexes could be formed.When the fibril content exceeded 9.09% wt.,the surface charge of the complexes decreased obviously and the turbidity rose,indicating the complexes started to aggregate.BLGF content was shown to be the crisis factor that effect the emulsifying properties of the complex.Few amount of BLGF(< 9.09%wt.)was benefit for the emulsifying capacity and the emulsion stability of the complex.While exceed BLGF(9.09%wt.)would result an emulsion with bigger droplet size and the formed emulsions were easier to flocculate.4.BLGF/Zein complex could be formed at special conditions.In the range of pH 3.0 to pH 7.0,zein particles could bound to the fibril surface to form the pearl-necklace-like structure though a anti-solvent sediment approach.At pH below 3.0 or above 8.0 however,effective combination could not occur.The formed complex showed to be surface active,and the dilatational modulus of the complex on oil-water interface was between the BLGF and zein.